Method apparatus and system for determining a thermal signature

ABSTRACT

A method of determining a thermal signature from thermal data associated with a body section is disclosed. The method comprises: segmenting the thermal data into a plurality of segments, and calculating a set of locations defining a contour, each location being central with respect to picture-elements associated with one segment, thereby determining the thermal signature based on the contour.

RELATED APPLICATIONS

This application is a National Phase of PCT Patent Application No.PCT/IL2009/001149 having International filing date of Dec. 3, 2009,which claims the benefit of priority of U.S. Provisional PatentApplication No. 61/193,504 filed on Dec. 4, 2008. The contents of theabove applications are all incorporated herein by reference.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to thermalimages and, more particularly, but not exclusively, to the analysis ofthermal images by determining a thermal signature within the images.

The use of imaging in diagnostic medicine dates back to the early 1900s.Presently there are numerous different imaging modalities at thedisposal of a physician allowing imaging of hard and soft tissues andcharacterization of both normal and pathological tissues.

Infra red imaging is utilized for characterizing a thermallydistinguishable site in a human body for the purposes of identifyinginflammation. Infrared cameras produce two-dimensional images known asthermographic images. A thermographic image is typically obtained byreceiving from the body of the subject radiation at any one of severalinfrared wavelength ranges and analyzing the radiation to provide atwo-dimensional temperature map of the surface. The thermographic imagecan be in the form of either or both of a visual image and correspondingtemperature data. The output from infrared cameras used for infraredthermography typically provides an image comprising a plurality of pixeldata points, each pixel providing temperature information which isvisually displayed, using a color code or grayscale code. Thetemperature information can be further processed by computer software togenerate for example, mean temperature for the image, or a discrete areaof the image, by averaging temperature data associated with all thepixels or a sub-collection thereof.

Based on the thermographic image, a physician diagnoses the site, anddetermines, for example, whether or not the site includes aninflammation while relying heavily on experience and intuition.

U.S. Pat. No. 7,072,504 discloses an approach which utilizes twoinfrared cameras (left and right) in combination with two visible lightcameras (left and right). The infrared cameras are used to provide athree-dimensional thermographic image and the visible light cameras areused to provide a three-dimensional visible light image. Thethree-dimensional thermographic and three-dimensional visible lightimages are displayed to the user in an overlapping manner.

International Patent Publication No. 2006/003658, the contents of whichare hereby incorporated by reference, discloses a system which includesnon-thermographic image data acquisition functionality and thermographicimage data acquisition functionality. The non-thermographic image dataacquisition functionality acquires non-thermographic image data, and thethermographic image data acquisition functionality acquiresthermographic image data.

U.S. Pat. No. 7,292,719, the contents of which are hereby incorporatedby reference discloses a system for determining presence or absence ofone or more thermally distinguishable objects in a living body. Acombined image generator configured combines non-thermographicthree-dimensional data of a three-dimensional tissue region in theliving body with thermographic two-dimensional data of the tissue regionso as to generate three-dimensional temperature data associated with thethree-dimensional tissue region.

Also of interest is U.S. Pat. No. 6,442,419 disclosing a scanning systemincluding an infrared detecting mechanism which performs a 360° dataextraction from an object, and a signal decoding mechanism, whichreceives electrical signal from the infrared detecting mechanism andintegrates the signal into data of a three-dimensional profile curvedsurface and a corresponding temperature distribution of the object.

Additional background art includes U.S. Pat. No. 6,850,862 whichdiscloses the generation of three-dimensional maps of temperaturedistribution, and U.S. Pat. No. 5,961,466 which discloses detection ofbreast cancer from a rapid time series of infrared images which isanalyzed to detect changes in the distribution of thermoregulatoryfrequencies over different areas of the skin.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present inventionthere is provided a method of determining a thermal signature fromthermal data associated with a body section, the thermal data beingarranged gridwise in a plurality of picture-elements representing athermal image, the method comprising: segmenting the thermal data into aplurality of segments; and calculating a set of locations defining acontour, each location being central with respect to picture-elementsassociated with one segment; thereby determining the thermal signaturebased on the contour.

According to an aspect of some embodiments of the present inventionthere is provided a method of determining presence or absence of athermally distinguished region in a body section, comprising:determining a thermal signature of the body section as described above,and comparing the thermal signature with a reference thermal signatureso as to determine the presence or absence of the thermallydistinguished region.

According to an aspect of some embodiments of the present inventionthere is provided a method of determining presence or absence of athermally distinguished region in a body section, comprising:determining a thermal signature of the body section as described above;and employing a comparison procedure for searching a library ofreference thermal signatures for a reference thermal signature similarto the thermal signature of the body section so as to determine thepresence or absence of the thermally distinguished region.

According to an aspect of some embodiments of the present inventionthere is provided a method of monitoring evolution of a thermallydistinguished region in a body section, comprising: obtaining a seriesof thermal images of the body section; for each thermal image,determining a thermal signature of the body section as described above;and comparing at least two of the thermal signatures, and using thecomparison for assessing changes in the thermally distinguished region,thereby monitoring the evolution of the thermally distinguished region.

According to an aspect of some embodiments of the present inventionthere is provided a method of monitoring evolution of a thermallydistinguished region in a body section having a surface, comprising:generating a series of thermospatial representations of the bodysection, each representation having thermal data of the body sectionassociated with spatial data representing the surface; for eachthermospatial representation, determining a thermal signature of thebody section as described above; and comparing at least two of thethermal signatures, and using the comparison for assessing changes inthe thermally distinguished region, thereby monitoring the evolution ofthe thermally distinguished region.

According to an aspect of some embodiments of the present inventionthere is provided a method of comparing a thermospatial representationof a body section with a reference thermospatial representation of areference body section, each thermospatial representation having thermaldata of a respective body section associated with spatial datadescribing a surface of the respective body section, the methodcomprising: for each thermospatial representation, segmenting thethermal data into a plurality of segments, and determining a morphologyassociated with at least one of the segments based on the thermal dataof the thermospatial representation; comparing respective morphologiesamongst the thermospatial representations; and using the comparison fordetermining the presence or absence of a thermally distinguished regionin the body section.

According to some embodiments of the present invention the thermallydistinguished region is a tumor and the method further comprisesapplying a destructive treatment to the tumor, wherein the comparison isused for assessing whether the size of the tumor is stable.

According to some embodiments of the present invention the comparisoncomprises contour alignment.

According to some embodiments of the present invention the methodfurther comprises assigning weights for at least some picture-elementsof the spatial data, wherein the calculation of the set of locations isbased on the weights.

According to some embodiments of the invention the assignment of weightscomprises performing spatial derivatives.

According to some embodiments of the invention the method furthercomprises defining a region-of-interest within the body section whereinthe calculation of the set is performed only over theregion-of-interest.

According to some embodiments of the invention the spatial datacomprises data representing a surface of tissue being nearby to the bodysection and the method comprises defining a spatial boundary between thesurface of the body section and the surface of the nearby tissue.

According to an aspect of some embodiments of the present inventionthere is provided apparatus for determining a thermal signature fromthermal data associated with a body section, the thermal data beingarranged gridwise in a plurality of picture-elements representing athermal image, the apparatus comprising: a segmentation unit, forsegmenting the thermal data into a plurality of segments; a locationcalculator, for calculating a set of locations defining a contour, eachlocation being central with respect to picture-elements associated withone segment.

According to some embodiments of the invention the thermal data isassociated with spatial data describing a surface of the body section,hence forming, together with the spatial data a thermospatialrepresentation of the body section, and wherein at least one location ofthe set represents a volume-element.

According to an aspect of some embodiments of the present inventionthere is provided an imaging and processing system, comprising: athermospatial imaging system operable to provide a thermospatialrepresentation of a body section having a surface, the thermospatialrepresentation having thermal data of the body section associated withspatial data describing the surface; and the apparatus for determining athermal signature.

According to some embodiments of the present invention the apparatusfurther comprises a weights assigner for assigning weights for at leastsome picture-elements, and wherein the location calculator is operableto calculate the set of locations based on the weights.

According to some embodiments of the invention the weights assigner isoperable to employ an edge detection procedure.

According to some embodiments of the invention each location is aweighted average of picture-element associated with one segment.

According to some embodiments of the present invention the apparatusfurther comprises an analysis unit operable to compare the thermalsignature with a reference thermal signature.

According to some embodiments of the invention the analysis unit isconfigured for employing a comparison procedure and accessing a libraryof thermal signatures for searching the library for a reference thermalsignature similar to the thermal signature of the body section.

According to some embodiments of the present invention the analysis unitis operable to employ contour alignment for the comparison.

According to some embodiments of the present invention the spatial datacomprises data representing a surface of tissue being nearby to the bodysection and the apparatus comprises a boundary definition unit fordefining a spatial boundary between the surface of the body section andthe surface of the nearby tissue.

According to some embodiments of the present invention the contour isplanar.

According to some embodiments of the present invention the contour isnon-planar.

According to some embodiments of the present invention the the contouris branched.

According to some embodiments of the present invention the the contouris non-branched.

According to some embodiments of the present invention the the contouris continuous.

According to some embodiments of the present invention the the contouris discontinuous.

According to some embodiments of the present invention the referencethermal signature corresponds to a reference body section other than thebody section and being similar in shape thereto.

According to some embodiments of the present invention the referencethermal signature comprises history data of the body section.

According to some embodiments of the present invention the body sectionis a first breast of a subject and the reference body section is asecond breast of the subject.

According to an aspect of some embodiments of the present inventionthere is provided a method of identifying blood vessels in a thermalimage of a section of a living body, the method comprising: convolvingintensity data representing the thermal image with a predeterminedvessel shapes filter thereby providing filtered data; calculating localderivatives of the filtered data along at least two dimensions, therebyproviding derivative data; searching in the derivative data for localintensity extrema; and applying an interpolation procedure forgenerating contours between at least a few of the local intensityextrema, and identifying the contours as blood vessels.

According to some embodiments of the invention the method furthercomprises, prior to the convolution, inverting the intensity data bylinear transformation.

According to some embodiments of the invention the method furthercomprises masking the intensity data so as to exclude at least a portionof the intensity data, the portion corresponding to picture-elements notbelonging to blood vessels.

According to some embodiments of the invention the masking comprisescalculating at least one of: local minimum, local maximum and localaverage for each picture-element of the thermal image.

According to some embodiments of the present invention the methodfurther comprises normalizing the intensity data.

According to some embodiments of the present invention the calculationof the local derivatives comprises: calculating local derivatives alonga first dimension; calculating local derivatives along a seconddimension; and for each picture-element of the thermal image, selectingthe highest of a respective derivative along the first direction and arespective derivative along the second direction.

According to some embodiments of the present invention the methodfurther comprises, subsequently to the search for local intensityextrema, employing a noise reduction procedure for excluding isolatedlocal intensity extrema.

According to some embodiments of the present invention the methodfurther comprises generating a blood vessel map based on the identifiedblood vessels.

According to an aspect of some embodiments of the present inventionthere is provided a method of recognizing an individual based on a bodysection of the individual, comprising: identifying blood vessels in athermal image of the body section, so as to generate a blood vessel map;searching a searchable database of blood vessel maps for a map entrywhich is similar to the blood vessel map; and identifying the individualbased on the map entry.

According to an aspect of some embodiments of the present inventionthere is provided a method of estimating characteristic heat conductionof a section of a living body, comprising: obtaining a series ofthermospatial representations describing the section of the living bodywhile having at least two different shapes; for each shape, identifyingat least one blood vessel in thermal data of a respective thermospatialrepresentation and calculating a depth of the at least one blood vessel;determining thermal stabilization period for the at least one bloodvessel; and determining the characteristic heat conduction based atleast in part on the thermal stabilization period.

According to an aspect of some embodiments of the present inventionthere is provided apparatus for identifying blood vessels in a thermalimage of a section of a living body, the apparatus comprising: aconvolution unit, for convolving intensity data representing the thermalimage with a predetermined vessel shapes filter thereby to providefiltered data; a derivative calculator, for calculating localderivatives of the filtered data along at least two dimensions, therebyproviding derivative data; a local intensity extrema searcher, forsearching in the derivative data for local intensity extrema; and aninterpolator, for applying an interpolation procedure for generatingcontours between at least a few of the local intensity extrema, andidentifying the contours as blood vessels.

According to some embodiments of the invention the apparatus furthercomprises an intensity data inverter for inverting the intensity data bylinear transformation.

According to some embodiments of the invention the apparatus furthercomprising a masking unit for masking the intensity data so as toexclude at least a portion of the intensity data, the portioncorresponding to picture-elements not belonging to blood vessels.

According to some embodiments of the invention the masking unit isoperable to calculate at least one of: local minimum, local maximum andlocal average for each picture-element of the thermal image.

According to some embodiments of the present invention the apparatusfurther comprises a normalization unit for normalizing the intensitydata.

According to some embodiments of the present invention the derivativecalculator is operable to: calculate local derivatives along a firstdimension; calculate local derivatives along a second dimension; and foreach picture-element of the thermal image, select the highest of arespective derivative along the first direction and a respectivederivative along the second direction.

According to some embodiments of the present invention the apparatusfurther comprises a noise reduction unit which employs a noise removalprocedure to exclude isolated local intensity extrema.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

Implementation of the method and/or system of embodiments of theinvention can involve performing or completing selected tasks manually,automatically, or a combination thereof. Moreover, according to actualinstrumentation and equipment of embodiments of the method and/or systemof the invention, several selected tasks could be implemented byhardware, by software or by firmware or by a combination thereof usingan operating system.

For example, hardware for performing selected tasks according toembodiments of the invention could be implemented as a chip or acircuit. As software, selected tasks according to embodiments of theinvention could be implemented as a plurality of software instructionsbeing executed by a computer using any suitable operating system. In anexemplary embodiment of the invention, one or more tasks according toexemplary embodiments of method and/or system as described herein areperformed by a data processor, such as a computing platform forexecuting a plurality of instructions. Optionally, the data processorincludes a volatile memory for storing instructions and/or data and/or anon-volatile storage, for example, a magnetic hard-disk and/or removablemedia, for storing instructions and/or data. Optionally, a networkconnection is provided as well. A display and/or a user input devicesuch as a keyboard or mouse are optionally provided as well.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIGS. 1A-C are schematic illustrations of a thermospatialrepresentation, according to some embodiments of the present invention;

FIG. 2 is a flow chart diagram of a method suitable for determining athermal signature of a body section, according to some embodiments ofthe present invention;

FIGS. 3A-B show boundaries definitions for a left breast (FIG. 3A) and aright breast (FIG. 3B), according to various exemplary embodiments ofthe present invention;

FIGS. 4A-B show a flip of a coordinate-system for a thermospatialrepresentation of a left breast (FIG. 4A) and a non-flippedcoordinate-system for a thermospatial representation of a right breast(FIG. 4B), according to various exemplary embodiments of the presentinvention;

FIGS. 5A-D illustrates sets of locations representing contours which canbe used for determining a thermal signature, according to variousexemplary embodiments of the present invention;

FIG. 6 shows a comparison between contours obtained according to someembodiments of the present invention for the left and right breastsillustrated in FIGS. 3A-B;

FIG. 7 is a flowchart diagram of a method suitable for determiningpresence or absence of a thermally distinguished region in a bodysection, according to various exemplary embodiments of the presentinvention;

FIGS. 8A-B show results of an exemplary implementation of the methodillustrated in FIG. 7 for the case of breasts of women;

FIG. 9 is a flowchart diagram of an additional method suitable fordetermining presence or absence of a thermally distinguished region in abody section, according to some embodiments of the present invention;

FIG. 10 which is a schematic illustration of apparatus for determining athermal signature of a body section, according to various exemplaryembodiments of the present invention;

FIG. 11 which is a schematic illustration of an imaging and processingsystem, according to various exemplary embodiments of the presentinvention;

FIGS. 12A-F and 13A-E are schematic illustration of a thermospatialimaging system, according to various exemplary embodiments of thepresent invention;

FIGS. 14 and 15 are flowchart diagrams of a method suitable foridentifying blood vessels in a thermal image of a section of a livingbody, according to various exemplary embodiments of the presentinvention;

FIGS. 16A-I and 17A-C are images obtained during the execution ofvarious operations of the method illustrated in FIGS. 14 and 15;

FIG. 18 is a fragmentary schematic illustration of a rectangular grid ofpicture-elements;

FIG. 19 which is a schematic illustration of an apparatus foridentifying blood vessels in a thermal image of a section of a livingbody, according to various exemplary embodiments of the presentinvention; and

FIG. 20 is a flowchart diagram of a method suitable for estimatingcharacteristic heat conduction, according to various exemplaryembodiments of the present invention; and

FIGS. 21A-F show representative segmentation operation, in accordancewith some embodiments of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to thermalimages and, more particularly, but not exclusively, to the analysis ofthermal images by determining a thermal signature within the images.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings and/or the Examples. The invention iscapable of other embodiments or of being practiced or carried out invarious ways.

The present inventors have devised an approach which enables theanalysis of a thermal image, e.g., for the purpose determining a thermalsignature of a body section. It was found by the present inventors thatthe thermal signature according to some embodiments of the presentinvention can be used to characterize the body section from thestandpoint of its thermal properties and optimally to compare the bodysection to another body section and/or the same body section at anearlier time.

The thermal signature of the present embodiments can be based on acontour of locations over the thermal image the body section.

The thermal signature of the present embodiments can be based on acontour of locations within the body section. The contour of locationsof the present invention can be planar or non-planar. In someembodiments of the present invention the thermal signature is a quantitywhich describes or characterizes the contour. This quantity can be theshape of the contour or a family of shapes to which the contour belongs.This quantity can also be a calculated quantity, such as a size or adensity associated with the contour. This quantity can also describesimilarity between the contour and a reference contour as furtherdetailed hereinunder.

In some embodiments of the present invention, the thermal signature canbe used for determining the likelihood for the presence of a thermallydistinguishable region in the body section. When the thermal image is ofa section of living body such as a breast of a male or female subject,the analysis of the present embodiments can be used to extractproperties of the underlying tissue. For example, determination of thelikelihood that a thermally distinguished region is present in the bodysection can be used for assessing whether or not the body section has apathology such as a tumor or an inflammation.

An elevated temperature is generally associated with a tumor due to themetabolic abnormality of the tumor and proliferation of blood vessels(angiogenesis) at and/or near the tumor. In a cancerous tumor the cellsproliferate faster and thus are more active and generate more heat. Thistends to enhance the temperature differential between the tumor itselfand the surrounding temperature. The present embodiments can thereforebe used for diagnosis of cancer, particularly, but not exclusivelybreast cancer.

The surface information used for the analysis comprises thermalinformation and optionally also spatial information.

The thermal information comprises data pertaining to heat evacuated fromor absorbed by the surface. Since different parts of the surfacegenerally evacuate or absorb different amount of heat, the thermalinformation comprises a set of tuples, each comprising the coordinatesof a region or a point on the surface and a thermal numerical value(e.g., temperature, thermal energy) associated with the point or region.The thermal information can be transformed to visible signals, in whichcase the thermal information is in the form of a thermographic image.

The thermal data is typically arranged gridwise in a plurality ofpicture-elements (e.g., pixels, arrangements of pixels) representing thethermographic image. Each picture-element is represented by an intensityvalue or a grey-level over the grid. It is appreciated that the numberof different intensity values can be different from the number ofgrey-levels. For example, an 8-bit display can generate 256 differentgrey-levels. However, in principle, the number of different intensityvalues corresponding to thermal information can be much larger. As arepresentative example, suppose that the thermal information spans overa range of 37° C. and is digitized with a resolution of 0.1° C. In thiscase, there are 370 different intensity values and the use ofgrey-levels is less accurate by a factor of approximately 1.4. Use ofhigher formats (e.g., 10 bit, 12 bit, 14 bit or higher) is alsocontemplated. For example, a photon thermal camera can provideinformation pertaining to the number of photons detected by the cameradetector. Such information can extend over a range of about 6000-8000intensity values.

In some embodiments of the present invention the processing of thermaldata is performed using intensity values, and in some embodiments of thepresent invention the processing of thermal data is performed usinggrey-levels. Combinations of the two (such as double processing) arealso contemplated.

The term “pixel” is sometimes abbreviated herein to indicate apicture-element. However, this is not intended to limit the meaning ofthe term “picture-element” which refers to a unit of the composition ofan image.

The terms “thermographic image”, “thermal image”, “thermal information”and “thermal data” are used interchangeably throughout the specificationwithout limiting the scope of the present invention in any way.Specifically, unless otherwise defined, the use of the term“thermographic image” is not to be considered as limited to thetransformation of the thermal information into visible signals. Forexample, a thermographic image can be stored in the memory of a computerreadable medium as a set of tuples as described above.

In embodiments in which the surface information also comprises spatialinformation, the spatial information comprises data pertaining togeometric properties of a surface which at least partially encloses athree-dimensional volume. In some embodiments of the present inventionthe surface is non-planar, e.g., curved. Generally, the surface is atwo-dimensional object embedded in a three-dimensional space. Formally,a surface is a metric space induced by a smooth connected and compactRiemannian 2-manifold. Ideally, the geometric properties of the surfacewould be provided explicitly for example, the slope and curvature (oreven other spatial derivatives or combinations thereof) for every pointof the surface. Yet, such information is rarely attainable and thespatial information is provided for a sampled version of the surface,which is a set of points on the Riemannian 2-manifold and which issufficient for describing the topology of the 2-manifold. Typically, thespatial information of the surface is a reduced version of a 3D spatialrepresentation, which may be either a point-cloud or a 3D reconstruction(e.g., a polygonal mesh or a curvilinear mesh) based on the point cloud.The 3D spatial representation is expressed via a 3D coordinate-system,such as, but not limited to, Cartesian, Spherical, Ellipsoidal, 3DParabolic or Paraboloidal coordinate 3D system.

The spatial data, in some embodiments of the present invention, can bein a form of an image. Since the spatial data represent the surface suchimage is typically a two-dimensional image which, in addition toindicating the lateral extent of body members, further indicates therelative or absolute distance of the body members, or portions thereof,from some reference point, such as the location of the imaging device.Thus, the image typically includes information residing on a surface ofa three-dimensional body and not necessarily in the bulk. Yet, it iscommonly acceptable to refer to such image as “a three-dimensionalimage” because the surface is conveniently defined over athree-dimensional system of coordinate. Thus, throughout thisspecification and in the claims section that follows, the terms“three-dimensional image” and “three-dimensional representation”primarily relate to surface entities.

The lateral dimensions of the spatial data are referred to as the x andy dimensions, and the range data (the depth or distance of the bodymembers from a reference point) is referred to as the z dimension.

When the surface information of a body comprises thermal information andspatial information, it the surface information (thermal and spatial) ofa body is typically in the form of a synthesized representation whichincludes both thermal data representing the thermal image and spatialdata representing the surface, where the thermal data is associated withthe spatial data (i.e., a tuple of the spatial data is associated with aheat-related value of the thermal data). Such representation is referredto as a thermospatial representation. The thermospatial representationcan be in the form of digital data (e.g., a list of tuples associatedwith digital data describing thermal quantities) or in the form of animage (e.g., a three-dimensional image color-coded or grey-level codedaccording to the thermal data). A thermospatial representation in theform of an image is referred to hereinafter as a thermospatial image.

The thermospatial image is defined over a 3D spatial representation ofthe body and has thermal data associated with a surface of the 3Dspatial representation, and arranged gridwise over the surface in aplurality of picture-elements (e.g., pixels, arrangements of pixels)each represented by an intensity value or a grey-level over the grid.

The term “voxel” is sometimes abbreviated herein to indicate avolume-element in the three-dimensional volume which is at leastpartially enclosed by the surface. However, this is not intended tolimit the meaning of the term “volume-element” which refers to a unit ofthe composition of a volume.

When the thermospatial representation is in the form of digital data,the digital data describing thermal properties can also be expressedeither in terms of intensities or in terms of grey-levels as describedabove. Digital thermospatial representation can also correspond tothermospatial image whereby each tuple corresponds to a picture-elementof the image.

Typically, one or more thermographic images are mapped or projected ontothe surface of the 3D spatial representation to form the thermospatialrepresentation. The thermographic image to be projected onto the surfaceof the 3D spatial representation preferably comprises thermal data whichare expressed over the same coordinate-system as the 3D spatialrepresentation. Any type of thermal data can be used. In one embodimentthe thermal data comprises absolute temperature values, in anotherembodiment the thermal data comprises relative temperature values eachcorresponding, e.g., to a temperature difference between a respectivepoint of the surface and some reference point, in an additionalembodiment, the thermal data comprises local temperature differences.Also contemplated, are combinations of the above types of temperaturedata, for example, the thermal data can comprise both absolute andrelative temperature values, and the like.

Typically, but not obligatorily, the information in the thermographicimage also includes the thermal conditions (e.g., temperature) at one ormore reference markers.

The acquisition of surface data is typically performed by positioningthe reference markers, e.g., by comparing their coordinates in thethermographic image with their coordinates in the 3D spatialrepresentation, to thereby match, at least approximately, also otherpoints hence to form the synthesized thermospatial representation.

The mapping of the thermographic image onto the surface of the 3Dspatial representation is effected by a calibration procedure.Optionally and preferably, the mapping of thermographic images isaccompanied by a correction procedure in which thermal emissivityconsiderations are employed.

The thermal emissivity of a body member is a dimensionless quantitydefined as the ratio between the amount of thermal radiation emittedfrom the surface of the body member and the amount of thermal radiationemitted from a black body having the same temperature as the bodymember. Thus, the thermal emissivity of an idealized black body is 1 andthe thermal emissivity of all other bodies is between 0 and 1. It iscommonly assumed that the thermal emissivity of a body is generallyequal to its thermal absorption factor.

The correction procedure can be performed using estimated thermalcharacteristics of the body of interest. Specifically, the thermographicimage is mapped onto a non-planar surface describing the body takinginto account differences in the emissivity of regions on the surface ofthe body. A region with a different emissivity value compared to itssurrounding, can be, for example, a scarred region, a pigmented region,a nipple region on the breast, a nevus. Additionally, the emissivityvalues of subjects with different skin colors may differ.

The correction procedure may also employ a heat distribution functiondescribing the distribution of heat away from a heat source located inof on the surface the body section. A heat distribution functionprovides the heat as a function of the distance and angle relative tothe heat source.

In some embodiments of the present invention, the thermographic image isweighted according to the different emissivity values of the surface.For example, when information acquired by a thermal imaging deviceinclude temperature or energy values, at least a portion of thetemperature or energy values can be divided by the emissivity values ofthe respective regions on the surface of the body. One of ordinary skillin the art will appreciate that such procedure results in effectivetemperature or energy values which are higher than the values acquiredby the thermal imaging device. Since different regions may becharacterized by different emissivity values, the weighted thermographicimage provides better estimate regarding the heat emitted from thesurface of the body.

A representative example of a synthesized thermospatial image for thecase that the body comprise the breasts of a female or male subject isillustrated in FIGS. 1A-C, showing a 3D spatial representationillustrated as a non-planar surface (FIG. 1A), a thermographic imageillustrated as planar isothermal contours (FIG. 1B), and a synthesizedthermospatial image formed by mapping the thermographic image on asurface of the 3D spatial representation (FIG. 1C). As illustrated, thethermal data of the thermospatial image is represented as grey-levelvalues over a grid generally shown at 102. It is to be understood thatthe representation according to grey-level values is for illustrativepurposes and is not to be considered as limiting. As explained above,the processing of thermal data can also be performed using intensityvalues. Also shown in FIGS. 1A-C, is a reference marker 101 whichoptionally, but not obligatorily, can be used for the mapping.

In some embodiments of the present invention a series of thermal imagesof a section of a living body is obtained. Different thermal images ofthe series include thermal data acquired from the body section atdifferent time instants. Such series of thermal images can be used bythe present embodiments to determine thermal changes occurred in thebody section over time.

In some embodiments of the present invention a series of thermospatialrepresentation of a section of a living body is obtained. Differentthermospatial representations of the series include thermal dataacquired from the body section at different time instants. Such seriesof thermospatial representations can be used by the present embodimentsto determine thermal and optionally spatial changes occurred in the bodysection over time.

The series can include any number of thermal images or thermospatialrepresentations. It was found by the inventors of the present inventionthat two thermal images or thermospatial representations are sufficientto perform the analysis, but more than two thermal images orthermospatial representations (e.g., 3, 4, 5 or more) can also be used,for example, to increase accuracy of the results and/or to allowselection of best acquisitions.

The 3D spatial representation, thermographic image and synthesizedthermospatial image can be obtained in any technique known in the art,such as the technique disclosed in International Patent Publication No.WO 2006/003658, U.S. Published Application No. 20010046316, and U.S.Pat. Nos. 6,442,419, 6,765,607, 6,965,690, 6,701,081, 6,801,257,6,201,541, 6,167,151, 6,167,151, 6,094,198 and 7,292,719.

Some embodiments of the invention can be embodied on a tangible mediumsuch as a computer for performing the method steps. Some embodiments ofthe invention can be embodied on a computer readable medium, comprisingcomputer readable instructions for carrying out the method steps. Someembodiments of the invention can also be embodied in electronic devicehaving digital computer capabilities arranged to run the computerprogram on the tangible medium or execute the instruction on a computerreadable medium. Computer programs implementing method steps of thepresent embodiments can commonly be distributed to users on a tangibledistribution medium. From the distribution medium, the computer programscan be copied to a hard disk or a similar intermediate storage medium.The computer programs can be run by loading the computer instructionseither from their distribution medium or their intermediate storagemedium into the execution memory of the computer, configuring thecomputer to act in accordance with the method of this invention. Allthese operations are well-known to those skilled in the art of computersystems.

FIG. 2 is a flow chart diagram of a method 10 suitable for determining athermal signature of a body section, according to some embodiments ofthe present invention. The body section can be one or more organs, e.g.,a breast or a pair of breasts, or a part of an organ, e.g., a part of abreast. In some embodiments of the present invention, the thermalsignature is determined by processing thermal data acquired from thesurface of the body section. In some embodiments of the presentinvention, the thermal signature is determined by processingthermospatial representation of the body section.

It is to be understood that, unless otherwise defined, the operations ofthe method described hereinbelow can be executed eithercontemporaneously or sequentially in many combinations or orders ofexecution. Specifically, the ordering of the flowchart diagrams is notto be considered as limiting. For example, two or more operations,appearing in the following description or in the flowchart diagrams in aparticular order, can be executed in a different order (e.g., a reverseorder) or substantially contemporaneously. Additionally, severaloperations method steps described below are optional and may not beexecuted.

The method begins at 11 and optionally continues to 12 at which thespatial and/or thermal data is preprocessed. In some embodiments of thepresent invention the preprocessing operation includes definition of oneor more spatial boundaries for the surface, so as to define aregion-of-interest for the analysis. This embodiment is particularlyuseful when the thermal signature is determined from a thermospatialrepresentation of the body section. For example, when the body sectionis a section of a living body and spatial data of the thermospatialrepresentation comprises data representing a surface of tissue beingnearby to the body section, the method preprocessing operation caninclude defining a spatial boundary between the surface of the bodysection and surface of the nearby tissue. In this embodiment, thesurface of the nearby tissue is preferably excluded from the analysis.FIGS. 3A-B exemplify boundaries definitions for the cases in which thebody section is a left breast (FIG. 3A) and a right breast (FIG. 3B).

In some embodiments of the present invention the preprocessing comprisestransformation of coordinates. For example, when the method is executedfor determining the thermal signature of more than one body sectionshaving similar shapes, the method preferably transform the coordinatesof one or more body section so as to ensure that all body sections aredescribed by the same coordinate-system. For example, when the methoddetermines the thermal signature of a left breast and a right breast,the system of coordinates of the thermal image and/or thermospatialrepresentation of one of the breasts can be flipped so as to describeboth thermal images and both thermospatial representations using thesame coordinate-system. FIGS. 4A-B exemplify a flip of acoordinate-system for a thermospatial representation of a left breast(FIG. 4A) and a non-flipped coordinate-system for a thermospatialrepresentation of a right breast (FIG. 4B).

In some embodiments of the present invention the preprocessing comprisesnormalization of the thermal data. The normalization is useful when itis desired not to work with too high values of intensities. In variousexemplary embodiments of the invention the normalization is performed soas to transform the range of thermal values within the thermal data to apredetermined range between a predetermined minimal thermal value and apredetermined maximal thermal value. This can be done using a lineartransformation as known in the art. A typical value for thepredetermined minimal thermal value is 1, and a typical value for thepredetermined maximal thermal value is 10. Other ranges or normalizationschemes are not excluded from the scope of the present invention.

In some embodiments of the present invention the preprocessing operationincludes slicing of the surface described by the spatial data to aplurality of slices. In these embodiments, the thermal signature can bedetermined separately for each slice. The slicing can be along a normaldirection (away from the body), parallel direction or azimuthaldirection as desired. The slicing can also be according to anatomicalinformation (for example a different slice for a nipple region). Alsocontemplated is arbitrary slicing, in which case the surface is slicedto N regions.

In some embodiments of the present invention the preprocessing comprisesnormalization of the spatial data. The normalization is useful when itis desired to compare between thermal signatures of different bodysections, for example, body sections having similar shapes but differentsizes. These embodiments are particularly useful when the body sectionis a breast and it is desired to compare the thermal signature ofbreasts of different sizes (e.g., a left breast to a right breast of thesame subject, or a breast of one subject to a breast of anothersubject).

In some embodiments of the present invention the method continues to 14at which the method assigns weights for at least some of thepicture-elements. The weights can be calculated based on Z dimension.Since the thermal and spatial data includes surface information, theweights are assigned to picture-elements which reside on the surface ofthe body section.

In various exemplary embodiments of the invention the weights areassigned by calculating spatial derivatives. For example, the method cancalculate a height gradient for the picture-elements with respect to oneor more lateral directions. Consider, for example, a picture-element pwhich belongs to a thermospatial representation and which is located atlocation (x, y, z), where x and y are the two lateral coordinates and zis a height coordinate. In the present embodiments, the method cancalculate at least one of the derivatives G_(x)=dz/dx and/orG_(y)=dz/dy. This can be done using any known image processingprocedure, such as, but not limited to, the by application of the Sobeloperator which is known in the art and described, e.g., in Sobel, I.,Feldman, G., “A 3×3 Isotropic Gradient Operator for Image Processing”,presented at a talk at the Stanford Artificial Project in 1968,unpublished but often cited, orig. in Pattern Classification and SceneAnalysis, Duda, R. and Hart, P., John Wiley and Sons, '73, pp271-2). Theweight w_(p) of picture-element p can be calculated using the calculatedderivatives. For example, when G_(x) is calculated, w_(p) can be set toG_(x), |G_(x)|, 1+|G_(x)|, √{square root over (1+G_(x) ²)}, etc.; whenG_(y) is calculated, w_(p) can be set to G_(y), |G_(y)|, 1+|G_(y)|,√{square root over (1+G_(y) ²)}, etc.; and when both G_(x) and G_(y) arecalculated w_(p) can be set to 1+|G_(x)|+|G_(y)|, √{square root over(1+G_(x) ²+G_(y) ²)}, etc.

The procedure can be repeated for at least some of the picture-elementsin the thermospatial representation, more preferably for all thepicture-elements under analysis. It is appreciated that in the aboveexample w_(p)>1 for all values of G_(x) and G_(y). Thus, in the presentembodiment the picture-elements are assigned with weights which aregreater than unity.

At 16 the method segments the thermal data. In embodiments in which themethod processes a thermal image, the segmentation is applied to thethermal data which represent the thermal image. In embodiments in whichthe method processes a thermospatial representation, the segmentation isapplied to the thermal data which forms, together with the spatial data,the thermospatial representation.

The result of the segmentation operation is a plurality of segments,each defined as a range of thermal values (intensities, grey levels ornormalized values in embodiments in which the normalization isemployed).

The segments are preferably mutually exclusives, namely that there is nooverlap between segments. Each thermal value over the thermal datapreferably belongs to one segment. Since the thermospatialrepresentation includes spatial data associated with the thermal data,each picture-element of the thermospatial representation is alsoassociated with one of the segments. Specifically, all picture-elementshaving thermal values which are within a range of thermal valuesdefining a particular segment are said to be associated with thatsegment. Formally, denoting the ith segment by s_(i) and the range ofthermal values which defines s_(i) by R_(i), the set P_(i) ofpicture-elements which are associated with s_(i) includes allpicture-elements which have a thermal value g satisfying g ε R_(i).

It is noted that the segmentation is of the thermal data and not thespatial data, although both type of data belong to the samethermospatial representation. Therefore, picture-elements which areassociated with a segment do not necessarily reside on the same regionof the surface. On the other hand, the thermal data of allpicture-elements associated with a segment are within the same range.FIGS. 21A-F show representative segmentation operation, in accordancewith some embodiments of the present invention. A different segment isshown in each of FIGS. 21A-F. As shown, picture-elements which areassociated with a segment may or may not reside on the same region ofthe surface.

The number of segments can be predetermined or it can be determined bythe method. The segmentation can be done according to the range ofvalues within the thermal data or within the portion of the thermal dataunder investigation or within the normalized thermal data. Thesegmentation can be uniform across the range of intensities. Forexample, when there are M different thermal values and N segments, eachsegment is defined over a range of approximately M/N thermal values.Without loss of generality, the thermal values can be integers from 1 toN. Denoting the N segments by s₁, s₂, . . . , s_(N), the first segments₁ can include thermal data values from 1 to approximately M/N, thesecond segment s₂ can include thermal data values from approximatelyM/N+1 to approximately 2M/N, etc. The special case in which N=M (i.e.,each segment is defined by a single thermal value) is not excluded fromthe scope of the present invention. Thus, the term “range of thermalvalues” as used herein also encompasses the case in which the rangeincludes a single thermal value.

The segmentation can also be non-uniform, in which case the range ofvalues for some segments is wider than the others. This embodiment isuseful when the uniform segmentation results in some segments which areassociated with a small number of picture-elements.

At 18 the method calculates a set of locations, which is subsequentlyused for determining the thermal signature of the body section. Inembodiments in which the method processes a thermal image, each of thelocations in the set can represent a picture-element of the thermalimage. In embodiments in which the method processes a thermospatialrepresentation each location can represent a surface-element (e.g., apixel) or a volume-element (e.g., a voxel) of the thermospatialrepresentation. For a given segment s_(i) (1≦i≦N) the method uses thespatial coordinates of the picture-elements associated with s_(i) (thepicture-elements in set P_(i)) to calculate a spatial location L_(i)which is central with respect to the locations of the picture-elementsin P_(i).

The location L_(i) can be calculated using any technique known in theart. Typically, the calculation involves some type of averagingprocedure, including, without limitation, arithmetic average, geometricaverage, harmonic average, root-mean-square, generalized (arbitrarypower) root-mean-power and the like. When the picture-elements in thethermal image, thermospatial representation or portion thereof areassigned with weights (see 14 in FIG. 2) the method preferablycalculates L_(i) as a weighted average of the locations of thepicture-element in the set P_(i). A weighted average can be viewed as atype of “center-of-mass” calculation whereby the weights of thepicture-elements in P_(i) play the role of the “masses” of thosepicture-elements. This description is particularly understood inembodiments in which the weights are correlated with the areas of thepicture-elements, because larger picture-elements can be considered asobjects of larger “masses”. The calculation the central locations can berepeated for several segments, more preferably for all segments, so asto provide a set of locations, each being central with respect to thepicture-element associated with one of the segments. The set oflocations represents a contour in a two-dimensional or athree-dimensional space. The contour can be planar or non-planar,branched or non-branched, continuous or discontinuous.

FIG. 5A shows a set 22 of locations 24 (10 locations are shown) whichrepresents a contour 26, in an embodiment in which the contour is aone-dimensional non-planar object embedded in a three-dimensional space.Although the contour is shown in FIG. 5A as a non-branched set of linesconnecting the locations, this need not necessarily be the case, sincein some embodiments of the present invention the contour can have one ormore branches. FIG. 5B shows contour 26 in an embodiment in whichcontour 26 is branched. In the representative example of FIG. 5B,contour 26 includes fives branches, generally shown at 28 a, 28 b, 28 c,28 d, and 28 e, where each branch is at one of the locations. FIGS. 5C-Dshow contour 26 in embodiments in which the contour is a one-dimensionalplanar object embedded in a two-dimensional space. In FIG. 5C contour 26is non-branched, and in FIG. 5D contour 26 is branched. In therepresentative example of FIG. 5D, contour 26 includes one branch,generally shown at 28.

While the lines connecting the locations are shown as straight lines inFIGS. 5A-D this need not necessarily be the case, since, for someapplications, it may be desired to form the contour using a fittingprocedure (e.g., a polynomial fit) in which case the lines can becurved.

In some embodiments of the present invention the contour is obtained inaccordance of the order of the thermal value ranges from which they werecalculated. Specifically, the first point of the contour correspond to asegment defined by the lowest range of thermal values, the second pointof the contour correspond to a segment defined by the next to lowestrange and so on. For example, consider a case in which there are Nthermal values 1, 2, . . . , N, and N segments s₁, s₂, . . . , s_(N),whereby s₁ is defined by the (single) thermal value 1, s₂ is defined bythe thermal value 2, and so on. In this case, the first point of thecontour corresponds to s₁, the second point of the contour correspondsto s₂, and so on. Consider another example in which there are 3N thermalvalues 1, 2, . . . , 3N and N segments s₁, s₂, . . . , s_(N), whereby s₁is defined by the range [1,3], s₂ is defined by the range [4,6] and soon. In this case, the first point of the contour corresponds to s₁, thesecond point of the contour corresponds to s₂, and so on.

The thermal signature of the present embodiments is based on contour 26.In some embodiments of the present invention the thermal signature is aquantity which describes or characterizes the contour. This quantity canbe the specific shape of the contour and/or a family of shapes (e.g.,planar/non-planar, closed/open, self intersecting/non-self intersecting,branched/non-branched) to which the contour belongs.

The thermal signature can also be a calculated quantity, such as a sizeassociated with the contour. For example, the thermal signature can bethe total length of the contour, the maximal or mean distance betweentwo points on the curve, and the like.

The thermal signature can also be a density associated with the contour.For example, a density can be defined as the number of picture-element,surface-elements and/or volume-elements which define the contour dividedby the total length of the contour.

The thermal signature can also be a vector which describes the Euclideandistance between the locations of successive picture-element,surface-elements and/or volume-elements which define the contour. Arepresentative example of such vector is (L₁L₂, L₂L₃, . . . ,L_(N−1)L_(N)) where L_(i)L_(i+1) (i=1, . . . , N−1) is the Euclideandistance between location L_(i) and location L_(i+1). This embodiment isparticularly useful in embodiments in which it is desired to compare twothermal signatures, as further detailed hereinbelow.

The method can also compare the thermal signature to a reference thermalsignature. The reference thermal signature generally corresponds to areference thermospatial representation, which can be obtained from alibrary or can be constructed by the method of the present embodiments.

The reference thermospatial representation can describe a reference bodysection other than the body section being analyzed. For example, thereference body section can be a body section which is similar in shapeto the body section being analyzed. When the body section is a breast,the reference body section can be the other breast of the same subject.In this embodiment, the aforementioned transformation of coordinates ispreferably employed so as to facilitate conceptual overlap of one bodysection over the other.

In some embodiments of the present invention the reference thermospatialrepresentation includes history data of the body section. Thus, thereference body section can be the same body section as captured at anearlier time. The inclusion of history data in the thermospatialrepresentation can be achieved by recording the reference thermospatialrepresentation and/or the thermal signature at a date earlier than thedate at which the method is executed. This embodiment can also be usefulfor monitoring changes in the body section over time.

When a series of thermospatial representations is obtained, thereference thermospatial representation can be one of the thermospatialrepresentations of the series. In some embodiments of the presentinvention the ambient temperature at the surface of the body section ischanged between two successive captures of surface information, and thecorresponding thermospatial representations are obtained. In theseembodiments, the thermal signatures of two such successive thermospatialrepresentations are determined and compared. Thus, in these embodiments,the reference thermal signature is the thermal signature whichcorresponds to the state of the body section prior to the change inambient temperature.

A change in the ambient temperature corresponds to different boundaryconditions for different thermospatial representations. Specifically, inthese embodiments, two successive thermospatial representations describethe body section while the subject is exposed to two different ambienttemperatures. A change in the ambient temperature can be imposed, forexample, by establishing contact between a cold object and the bodysection or directing a flow of cold gas (e.g., air) to the surface ofthe body section between successive data acquisitions. Also contemplatedis a procedure in which the body section is immersed in cold liquid(e.g., water) between successive data acquisitions. Also contemplated isa procedure in which another body section is exposed to a different(e.g., lower) temperature so as to ensure transient thermal condition.For example, the subject can immerse his or her limb in a cold liquid(e.g., water).

In some embodiments of the present invention the reference thermospatialrepresentation is obtained by means of biomedical engineering.

The comparison between the thermal signatures is typically according tothe way the thermal signature is determined based on the contour.

When the thermal signature is defined as the shape of the contour thecomparison is preferably done shape-wise. In this embodiment, thecontour and the reference contour are preferably defined in the samecoordinate-system. FIG. 6 shows a comparison between contours obtainedfor the left and right breasts illustrated in FIGS. 3A-B.

In various exemplary embodiments of the invention a contour or curvealignment procedure is employed for the comparison of the contour andthe reference contour. For example, the method can perform a pairwisecalculation of the distances between the locations defining the contourand the locations defining the reference contour, to provide a vector ofdistances. A representative example of such vector is (L₁L′₁, L₂L′₂, . .. , L_(N)L′_(N)) where L_(i)L′_(i) (i=1, . . . , N) is the Euclideandistance between location L_(i) in the contour and location L′_(i) inthe reference contour. A vector of distances can also be obtained whenthe vectors are of different lengths. In this case a dilution procedurefor one or both contour preferably precedes the calculation ofdistances.

Once a vector of distances is obtained the method can use the vector tocalculate a score which characterizes the similarity or dissimilaritybetween the thermal signatures. The score can include, for example,norm, mean and/or variance of the vector. The score can also include acombination between these quantities. In various exemplary embodimentsof the invention the score is the sum of squares of the mean andstandard deviation of the vector.

Once a vector of distances is obtained the method can calculate the normof this vector so as to quantify the similarity or dissimilarity betweenthe thermal signatures using a single score. It was found by the presentinventors that the similarity or dissimilarity between the thermalsignatures can be used to distinguish between different types of tumors(e.g., whether or not the thermally distinguished region is a tumor, orwhether the tumor is malignant or benign).

Other contour or curve alignment procedures are not excluded from thescope of the present invention. Representative examples of otherprocedures include, without limitation, the procedures disclosed inGareth M. James, Annals of Applied Statistics (2007) Vol. 1, No. 2480-501; and Peter J. Green and Kanti Mardia (2005), arXiv:math/0503712.

When the thermal signature is defined as a calculated quantity, suchsize density and the like, the comparison between the thermal signatureis based on the calculated quantity, wherein large deviations betweenthe respective calculated quantities correspond to high level ofdissimilarity between the thermal signatures and vice versa.

In some embodiments of the present invention the method compares themorphology associated with one or more segments with the morphologyassociated with the respective segments in the reference representation.Such comparison is optionally used by the method to determine similarityor dissimilarity between the two representations. For example, if thereference representation corresponds to a healthy body section and ahigh degree of similarity was found between the morphologies associatedwith respective segments, the method can determine that it is likelythat the body section under investigation is also healthy. On the otherhand is a high degree of dissimilarity was found between themorphologies associated with respective segments, the method candetermine that it is likely that the body section under investigationhas a thermally distinguished region.

The method ends at 20.

Reference is now made to FIG. 7 which is a flowchart diagram of a method30 suitable for determining presence or absence of a thermallydistinguished region in a body section, according to various exemplaryembodiments of the present invention.

The method begins at 31 and continues to 32 at which the methoddetermines a thermal signature in the body section, for example, usingselected operations of method 10. At 33 the method compares the thermalsignature with a reference thermal signature of a referencethermospatial representation as further detailed hereinabove.Preferably, the reference body section is devoid of thermallydistinguishable region.

The method continues to decision 34 at which the method determinewhether or not the thermal signature is similar to the reference thermalsignature. The similarity can be determined according to any of thecriteria described above. In various exemplary embodiments of theinvention the similarity is quantified by a score as further detailedhereinabove.

If the signatures are similar, the method continues to 35 at which themethod determines that a thermally distinguished region is not likely tobe present in the body section. If the signatures are dissimilar, themethod continues to 36 at which the method determines that a thermallydistinguished region is likely to be present in the body section.

The method ends at 37.

Exemplary implementation of method 30 as performed by the presentinventors for the case of breasts of women is shown in FIGS. 8A-B.

Thermospatial representations of two breasts were obtained. For eachthermospatial representation a contour was obtained as further detailedhereinabove. The two obtained contours (one for each breast) werecompared and a score was calculated to quantify the similarity betweenthe two contours. In the present experiments, the score was calculatedas the sum of squares of the mean and standard deviation of the vectorof distances between the two contours.

FIG. 8A demonstrates results of an experiment in which the two breastsof the woman subject were devoid of any thermally distinguished. The twoobtained contours are illustrated on the same system of coordinatestogether with a thermospatial representation of the left breast. Asshown, the two contours are substantially similar and it can bedetermined that a thermally distinguished region is not likely to bepresent in the breasts. The calculated score in this experiment was230.47.

FIG. 8B demonstrates results of an experiment in which the left breastof the woman subject included a thermally distinguished region and aright breast (of the same woman subject) was devoid of any thermallydistinguished region. The two obtained contours are illustrated on thesame system of coordinates together with a thermospatial representationof the left breast. As shown, the two contours are substantiallydissimilar and it can be determined that a thermally distinguishedregion is likely to be present in the left breast. The calculated scorein this experiment was 1701.64.

Generally, it was found by the inventors of the present invention thatwhen one breast is known to be devoid of a thermally distinguishedregion, and when the score is the sum of squares of the mean andstandard deviation of the vector of distances between the two contours,the method can determine that a thermally distinguished region is likelyto be present in the other breast when the score is above 1000. Alsocontemplated is a comparison between the score for one breast and thescore for another breast. If a first breast is known to be devoid of athermally distinguished region the method can determine that a thermallydistinguished region is likely to be present in the second breast if thescore of the second breast is significantly higher that than the scoreof the first breast.

Reference is now made to FIG. 9 which is a flowchart diagram of a method40 suitable for determining presence or absence of a thermallydistinguished region in a body section, according to some embodiments ofthe present invention.

The method begins at 41 and continues to 42 at which the methoddetermines a thermal signature in the body section, for example, usingselected operations of method 10. At 43 the method searches a library ofreference thermal signatures for a reference thermal signature which issimilar to the thermal signature of the body section.

At 44 the method determines the likelihood of presence of a thermallydistinguished region in the body section based on the reference thermalsignature found at 43. Specifically, if the reference thermal signatureis marked in the library as indicating for presence of thermallydistinguished region, the method determines that a thermallydistinguished region it is likely to be present. Conversely, if thereference thermal signature is marked in the library as indicating forabsence of thermally distinguished region, the method determines that athermally distinguished region it is not likely to be present. Thepresent embodiments also contemplate estimating the location of athermally distinguished region. For example, if the method determinesthat a thermally distinguished region is likely to be present, themethod compares the thermal signature to several reference thermalsignatures of reference body sections having thermally distinguishedregion at known locations. The result of these comparisons (e.g., bestfit) can be used for estimating the location of the thermallydistinguished region in the body section under analysis.

The method ends at 45.

The techniques of the present embodiments can also be implemented for soas to monitor the evolution of a thermally distinguished region in abody section. For example, if the thermal signature is substantiallydifferent from its value at an earlier date, the method can determinethat the changes in the thermally distinguishable region had occurred.This embodiment can also be useful for monitoring efficacy of treatment.For example, when a subject having a malignant tumor is treated withchemotherapy, the thermal signature can be determined at different timesso as to assess the efficacy of treatment.

Reference is now made to FIG. 10 which is a schematic illustration of anapparatus 50 for determining a thermal signature of a body section,according to some embodiments of the present invention. Apparatus 50 canbe implemented in a data processor or a computer system and can be usedfor executing one or more of the method steps described above. Data flowchannels between the various components of apparatus 50 are shown asarrows in FIG. 10.

In some embodiments of the present invention apparatus 50 comprises aninput unit 52 for receiving the spatial and/or thermal data. Forexample, input unit 52 can receive a thermospatial representation.Apparatus 50 comprises a segmentation unit 54 for segmenting the thermaldata into a plurality of segments, as further detailed hereinabove, anda location calculator 56, for calculating a set of locations defining acontour as further detailed hereinabove. Location calculator 56 receivesspatial data from unit 52.

In various exemplary embodiments of the invention apparatus 50 furthercomprises a weights assigner 58 for assigning weights for at least somepicture-elements of the spatial data, as further detailed hereinabove.Weights assigner 58 receives spatial data from unit 52 and provides theweights to location calculator 56.

In some embodiments of the present invention apparatus 50 comprises aslicing unit for slicing the surface to a plurality of slices. In theseembodiments, calculator 56 preferably receives the slices from slicingunit 60 and calculates the locations separately for each slice.

In some embodiments of the present invention apparatus 50 comprises aboundary definition unit 62 which defines the spatial boundary betweenthe surface of the body section and the surface of nearby tissue. Inthese embodiments, location calculator 56, preferably receives data fromunit 62 and excludes the surface of the nearby tissue from thecalculation of the set of locations. Optionally, boundary definitionunit 62 also communicates with slicing unit 60. For example, unit 62 canreceive the slices from unit 60 and define the region-of-interest basedon the slices. In some embodiments, unit 60 receives the boundaries fromunit 62 and calculates the slices after the region-of-interest has beendefined.

Apparatus 50 preferably comprises an output unit 64 which issues areport regarding the thermal signature. In some embodiments of thepresent invention apparatus 50 comprises an analysis unit 66 whichcompares the thermal signature with a reference thermal signature, asfurther detailed hereinabove. The analysis unit can access a library ofthermal signatures and search the library for a reference thermalsignature similar to the thermal signature, as further detailedhereinabove. Analysis unit 66 can employ contour alignment for thepurpose of comparison. Analysis unit 66 can provide the results of thecomparison to output unit 64, which includes the results in the report.The analysis performed by unit 66 can include the determination of thelikelihood that a thermally distinguishable region is present in thebody section, as further detailed hereinabove.

Reference is now made to FIG. 11 which is a schematic illustration of animaging and processing system 70, according to some embodiments of thepresent invention. System 70 comprises a thermospatial imaging system 72which provides a thermospatial representation of a body section, and ananalysis apparatus 74 for analyzing the thermospatial representation.The principles and operations of analysis apparatus 74 are similar tothe principles and operations of apparatus 50 described above. In someembodiments of the present invention apparatus 74 is apparatus 50.

The following description is of techniques for obtaining thethermospatial representation, according to various exemplary embodimentsof the present invention. The techniques described below can be employedby any of the method and apparatus described above.

A thermospatial representation or image can be generated obtained byacquiring one or more thermographic images and mapping the thermographicimage(s) on a 3D spatial representation.

Reference is now made to FIG. 12A which is a schematic illustration of athermospatial imaging system 120 in accordance with preferredembodiments of the present invention. As shown in FIG. 12A, a livingbody 210 or a part thereof of a person 212 is located in front of animaging device 214. The person 212, may be standing, sitting or in anyother suitable position relative to imaging device 214. Person 212 mayinitially be positioned or later be repositioned relative to imagingdevice 214 by positioning device 215, which typically comprises aplatform moving on a rail, by force of an engine, or by any othersuitable force. Additionally, a thermally distinguishable object 216,such as a tumor, may exist in body 210 of person 212. For example, whenbody 210 comprises a breast, object 216 can be a breast tumor such as acancerous tumor.

In accordance with a preferred embodiment of the present invention,person 212 may be wearing a clothing garment 218, such as a shirt.Preferably, clothing garment 218 may be non-penetrable or partiallypenetrable to visible wavelengths such as 400-700 nanometers, and may bepenetrable to wavelengths that are longer than visible wavelengths, suchas infrared wavelengths. Additionally, a reference mark 220 may belocated close to person 212, preferably directly on the body of person212 and in close proximity to body 210. Optionally and preferably,reference mark 220 is directly attached to body 210. Reference mark 220may typically comprise a piece of material, a mark drawn on person 212or any other suitable mark, as described herein below.

Imaging device 214 typically comprises at least one visible lightimaging device 222 that can sense at least visible wavelengths and atleast one thermographic imaging device 224 which is sensitive toinfrared wavelengths, typically in the range of as 3-5 micrometer and/or8-12 micrometer. Typically imaging devices 222 and 224 are capable ofsensing reference mark 220 described hereinabove.

Optionally, a polarizer 225 may be placed in front of visible lightimaging device 222. As a further alternative, a color filter 226, whichmay block at least a portion of the visible wavelengths, may be placedin front of visible light imaging device 222.

Typically, at least one visible light imaging device 222 may comprise ablack-and-white or color stills imaging device, or a digital imagingdevice such as CCD or CMOS. Additionally, at least one visible lightimaging device 222 may comprise a plurality of imaging elements, each ofwhich may be a three-dimensional imaging element. Device 222 can alsocomprise a video projector. This embodiment is particularly useful whenit is desired to employ the coded light technique (see, e.g., Sato etal, hereinafter) for building a 3D spatial representation.

Optionally and preferably, imaging device 214 may be repositionedrelative to person 212 by positioning device 227. As a furtheralternative, each of imaging devices 222 and 224 may also berepositioned relative to person 212 by at least one positioning device228. Positioning device 227 may comprise an engine, a lever or any othersuitable force, and may also comprise a rail for moving imaging device214 thereon. Preferably, repositioning device 228 may be similarlystructured.

Data acquired by visible light imaging device 222 and thermographicimaging device 224 is output to a data processor 230 via acommunications network 232, and is typically analyzed and processed byan algorithm running on the data processor. The resulting data may bedisplayed on at least one display device 234, which is preferablyconnected to data processor 230 via a communications network 236. Dataprocessor 230 typically comprises a PC, a PDA or any other suitable dataprocessor. Communications networks 232 and 236 typically comprise aphysical communications network such as an internet or intranet, or mayalternatively comprise a wireless network such as a cellular network,infrared communication network, a radio frequency (RF) communicationsnetwork, a blue-tooth (BT) communications network or any other suitablecommunications network.

In accordance with a preferred embodiment of the present inventiondisplay 234 typically comprises a screen, such as an LCD screen, a CRTscreen or a plasma screen. As a further alternative display 234 maycomprise at least one visualizing device comprising two LCDs or twoCRTs, located in front of a user's eyes and packaged in a structuresimilar to that of eye-glasses. Preferably, display 234 also displays apointer 238, which is typically movable along the X, Y and Z axes of thedisplayed model and may be used to point to different locations orelements in the displayed data.

Reference is now made to FIGS. 12B-F and 13A-E which illustrate thevarious operation principles of thermospatial imaging system 120, inaccordance with various exemplary embodiments of the invention.

The visible light imaging is described first, with reference to FIGS.12B-F, and the thermographic imaging is described hereinafter, withreference to FIGS. 13A-E. It will be appreciated that the visible lightimage data acquisition described in FIGS. 12B-F may be performed before,after or concurrently with the thermographic image data acquisitiondescribed in FIGS. 13A-E.

Referring to FIGS. 12B-F, person 212 comprising body 210 is located onpositioning device 215 in front of imaging device 214, in a firstposition 240 relative to the imaging device. First image data of body210 is acquired by visible light imaging device 222, optionally throughpolarizer 225 or as an alternative option through color filter 226. Theadvantage of using a color filter is that it can improve thesignal-to-noise ratio, for example, when the person is illuminated witha pattern or mark of specific color, the color filter can be used totransmit only the specific color thereby reducing background readings.Additionally, at least second image data of body 210 is acquired byvisible light imaging device 222, such that body 210 is positioned in atleast a second position 242 relative to imaging device 214. Thus, thefirst, second and optionally more image data are acquired from at leasttwo different viewpoint of the imaging device relative to body 210.

The second relative position 242 may be configured by repositioningperson 212 using positioning device 215 as seen in FIG. 12B, byrepositioning imaging device 214 using positioning device 227 as seen inFIG. 12C or by repositioning imaging device 222 using positioning device228 as seen in FIG. 12D. As a further alternative, second relativeposition 242 may be configured by using two separate imaging devices 214as seen in FIG. 12E or two separate visible light imaging device 222 asseen in FIG. 12F.

Referring to FIGS. 13A-E, person 212 comprising body 210 is located onpositioning device 215 in front of imaging device 214, in a firstposition 244 relative to the imaging device. First thermographic imagedata of body 210 is acquired by thermographic imaging device 224.Optionally and preferably at least second thermographic image data ofbody 210 is acquired by thermographic imaging device 224, such that body210 is positioned in at least a second position 242 relative to imagingdevice 214. Thus, the first, second and optionally more thermographicimage data are acquired from at least two different viewpoints of thethermographic imaging device relative to body 210.

The second relative position 246 may be configured by repositioningperson 212 using positioning device 215 as seen in FIG. 13A, byrepositioning imaging device 214 using positioning device 227 as seen inFIG. 13B, or by repositioning thermographic imaging device 224 usingpositioning device 228 as seen in FIG. 13C. As a further alternative,the second relative position 246 may be configured by using two separateimaging devices 214 as seen in FIG. 13D or two separate thermographicimaging devices 224 as seen in FIG. 13E.

Image data of body 210 may be acquired by thermographic imaging device224, by separately imaging a plurality of narrow strips of the completeimage of body 210. Alternatively, the complete image of body 210 isacquired by the thermographic imaging device, and the image is sampledin a plurality of narrow strips or otherwise shaped portions forprocessing. As a further alternative, the imaging of body 210 may beperformed using different exposure times.

The thermographic and visible light image data obtained from imagingdevice 214 is preferably analyzed and processed by data processor 230 asfollows. Image data acquired from imaging device 222 is processed bydata processor 230 to build a three-dimensional spatial representationof body 210, using algorithms and methods that are well known in theart, such as the method described in U.S. Pat. No. 6,442,419 or Sato etal., “Three-dimensional Surface Measurement by Space Encoding RangeImaging, Journal of Robotic Systems (1985) 27-39, the contents of whichis hereby incorporated by reference as if fully set forth herein. The 3Dspatial representation preferably comprises the location of referencemarker 220 (cf. FIG. 1A). Optionally and preferably, the 3D spatialrepresentation comprises information relating to the color, hue andtissue texture of body 210. Thermographic image data acquired fromimaging device 224 is processed by data processor 230 to build athermographic three-dimensional model of body 210, using algorithms andmethods that are well known in the art, such as the method described inU.S. Pat. No. 6,442,419. The thermographic 3D model preferably comprisesreference marker 220 (cf. FIG. 1B). The thermographic 3D model is thenmapped by processor 230 onto the 3D spatial representation, e.g., byaligning reference marker 220, to form the thermospatial image.

The present embodiments are also useful for constructing blood vesselsmap or for determining the location a specific blood vessel within thebody because the temperature of the blood vessel is generally differentfrom the temperature of tissue. In this respect, the present embodimentsare also useful in the area of face recognition, because the knowledgeof blood vessel positions in the face may aid in the identification ofcertain individuals. Recognition of other organs is also contemplated.Organ recognition using the present embodiments is particularlyadvantageous due to the ability of the present embodiments to localizethermally distinguishable regions in the living body. Such localizationcan be used for constructing blood vessel map which provides informationregarding both orientation and depth of blood vessels in the body. Themap can then be used for identifying individuals, e.g., by searching forsimilar map on a accessible and searchable database of blood vesselmaps. The map can also be an additional indicator for existence and/orlocation of tumors in the body section.

Reference is now made to FIG. 14 which is a flowchart diagram of amethod 300 suitable for identifying blood vessels in a thermal image ofa section of a living body. The method begins at 310 and continues to320 at which the method performs convolution of intensity datarepresenting the thermal image (e.g., intensity data, variance, changesover time, etc.) with a predetermined vessel shapes filter therebyproviding filtered data.

The present inventors have investigated the form of several bloodvessels that appear in different areas of the body. By comparing thecorrelation coefficient between all pattern samples, the presentinventor successfully defined several types of vessel patterns. Thepredetermined vessel shapes filter of the present embodiments includesthis information. In some embodiments of the present invention themethod convolves the rows and columns of the thermal image with a matrixof a vessel pattern. Typically, the vessel pattern matrix is a 4×4matrix, but other sizes of matrices are not excluded from the scope ofthe present invention.

At 330 the method calculates local derivatives of the filtered dataalong at least two dimensions to providing derivative data. The localderivatives are typically with respect to the lateral dimensions (the xand y dimensions in the present coordinate-system). In various exemplaryembodiments of the invention the derivatives are calculated separatelyfor each dimension, and the method selects the highest derivative foreach picture-element of the thermal image. The procedure can bedescribed as follows. Firstly, the derivative is implemented in onedirection (say the x direction) to provide a first derivative image.Secondly the derivative is implemented in another direction (say the ydirection) to provide a second derivative image. Thirdly, the methodcompares the two images pixel-by-pixel and selects the highest of thetwo derivatives for each pixel. It was found by the present inventorsthat this operation can reveal the morphology of blood vessels in thethermal image. This operation provides a morphology which can bedescribed as a system of ridges (local maxima) that divides areasdrained by different grooves (local minima) as blood vessels.

At 340 the method searches the derivative data for local intensityextrema, and at 305 the method applies an interpolation procedure forgenerating contours between at least a few of the local intensityextrema. In various exemplary embodiments of the invention the generatedcontours are identified as blood vessels.

The method ends at 350.

In some embodiments of the present invention method 300 comprises one ormore additional operations. These embodiments will now be explained withreference to FIGS. 15, 16A-I, 17A-C and 18.

FIG. 15 is a flowchart diagram describing method 300 according to someembodiments of the present invention. The method begins at 310 andoptimally continues to 311 at which the intensity data is normalized.The normalization can be according to any scheme known in the art. Invarious exemplary embodiments of the invention mean normalization isemployed. In these embodiments, the global mean of the all image issubtracted from each picture-element of the image. Also contemplatedare: subtraction or division of global minimum or maximum, midrangepreserving normalization, and the like. The result of mean normalizationis shown in FIG. 16A in the form of a two-dimensional image.

The method optionally continues to 312 at the method inverts theintensity data by linear transformation. This operation is known in theart and includes the transformation I→I_(max)−I, where I is theintensity value and I_(max) is the maximal intensity value. Inembodiments in which the normalization operation is performed, I is thenormalized intensity and I_(max) is the maximal normalized intensity.The result of the inversion operation is shown in FIG. 16B in the formof a two-dimensional image.

The method optionally continues to 313 at which the method masks theintensity data so as to exclude at least a portion of the intensitydata, where the excluded portion corresponds to picture-elements notbelonging to blood vessels. In embodiments in which normalization ispreferably employed the masking operation is performed on the normalizeddata. The masking can be done by calculating at least one of: localminimum, local maximum and local average for each picture-element of thethermal image. These local quantities are preferably calculated usingthe intensity values of the picture-element and at least a few of itsneighbors.

In various exemplary embodiments of the invention a moving window scansthe image. At each location of the moving window, one or more localstatistical quantities such as, but not limited to, minimum intensity,maximum intensity and mean intensity are calculated over the window andare assigned to the picture-element located at the center of the window.The procedure results in one statistical image per calculated quantity,where in each image, each picture-element contains the calculated valueof the respective quantity. FIGS. 17A-C show statistical images obtainedafter calculation of local minimum (FIG. 17A), local maximum (FIG. 17B),and mean (FIG. 17C) for a 3×3 moving window. Other sizes of movingwindows are also contemplated.

The masking can also include calculation of global quantities, such as,but not limited to, global minimum, global maximum and global meanvalues for each of the statistical images. In various exemplaryembodiments of the invention a set of comparisons queries between thevalues of the global quantities and the three statistical images,normalized and negative image to provide a binary masking image in whichpicture-element that are candidate for belonging to a blood vessel aremarked. For example, the binary masking image can includes 1's and 0'swhere candidate picture-elements are assigned with 1's while all otherpicture-element are assigned with 0's. Typically the masking image doesnot include edge values that usually belong to background or skin folds.

Following are some exemplified embodiments for the construction of themasking image. Each of the exemplified embodiments below can be employedeither singly or in combination with one or more other embodiments. Theemployment of all the exemplified embodiments below is alsocontemplated. The embodiments below are provided only for illustrativepurposes and should not be construed in any limiting way. In fact, thosereasonably skilled in the art of image processing will understand thatthe masking image can be constructed using other procedures orcombination of procedures.

In some embodiments of the present invention a picture-element in themasking image is assigned with “1” if the intensity value of acorresponding picture-element in the local minimum image is below apredetermined threshold. Such threshold can be approximately or a fewpercents below the global maximum value of the local minimum image.

In some embodiments of the present invention a picture-element in themasking image is assigned with “1” if the intensity value of acorresponding picture-element in the local maximum image is below apredetermined threshold. Such threshold can be approximately or somepercents above the global mean of the local maximum image.

In some embodiments of the present invention a picture-element in themasking image is assigned with “1” if the intensity value of acorresponding picture-element in the mean image is below a predeterminedthreshold. Such threshold can be approximately or some percents abovethe global mean of the local minimum image.

In some embodiments of the present invention a picture-element in themasking image is assigned with “1” if the intensity value of acorresponding picture-element in the mean image is above a predeterminedthreshold. Such threshold can be approximately the global minimum of thelocal maximum image.

In some embodiments of the present invention a picture-element in themasking image is assigned with “1” if the intensity value of acorresponding picture-element in the inverted image is below apredetermined threshold. Such threshold can be approximately theintensity value of a corresponding picture-element in the local maximumimage.

In some embodiments of the present invention a picture-element in themasking image is assigned with “1” if the intensity value of acorresponding picture-element in the normalized image is within apredetermined threshold. Such threshold can be approximately or a fewpercents above the minimal intensity value of the normalized image.

In some embodiments of the present invention a picture-element in themasking image is assigned with “1” if the intensity value of acorresponding picture-element in the normalized image is within apredetermined threshold. Such threshold can be approximately or severaltimes the mean intensity value of the normalized image.

FIG. 16C shows the obtained masking image, in embodiments in which thestatistical images of FIGS. 17A-C as well as their global minimum,maximum and mean values are employed during the masking operation.

At 320 the method performs convolution with a predetermined vesselshapes filter as further detailed hereinabove. In embodiments in whichinversion is employed, the convolution operation is preferably performedon the inverted intensity data. The advantage of operating on theinverted data is that is provides better visualization. FIG. 16D showsthe result of the convolution in the form of a two-dimensional image, inthe embodiments in which the vessel shapes filter is convoluted with theinverted intensity data.

At 330 the method calculates local derivatives of the filtered dataalong at least two dimensions as further detailed hereinabove. FIG. 16Eshows the local derivative data of FIG. 16D in a form of atwo-dimensional image.

At 340 the method searches the derivative data for local intensityextrema. When the convolution with the vessel shapes filter is performedusing the inverted data, the method preferably searches for localintensity minima. When the convolution with the vessel shapes filter isperformed using the inverted data, the method preferably searches forlocal intensity maxima. When a masking image is constructed, the methodpreferably perform the search only among picture-element which aremarked by the masking image as candidates for belonging to a bloodvessel.

The search preferably employs a moving window, e.g., a 3×3 moving windowwhich allows comparison of the intensity value of each picture-elementwith the intensity values of its eight immediate neighbors. Other sizesof moving window are also contemplated.

The search for extrema can be accompanied by a set of criteria. In someembodiments of the present invention the method calculates gradients ofintensities over a range of picture-element in the vicinity of thepicture-element under analysis and decides, based on the gradient,whether the picture-element is at a local extremum of intensities.Typical range for the calculation of gradients is about fourpicture-elements from the picture-element under analysis. A procedureaccording to some embodiments of the present invention can be betterunderstood with reverence to FIG. 18 which is a fragmentary schematicillustration of a rectangular grid of picture-elements. The ordinarilyskilled person would know how to adjust the description tonon-rectangular grids which are not excluded from the scope of thepresent invention.

Shown in FIG. 18 is a central picture-element 400 which is thepicture-element under analysis, and other picture-elements in thevicinity of element 400. Also shown in FIG. 18 is a two-dimensionalCartesian coordinate-system. The four nearest neighbors to element 400(along the x and y directions) are designated by reference sign 401, thefour next-to-nearest neighbors picture-element (nearest neighbors alonga diagonal) are designated by reference sign 402. Picture-elements in alayer immediately surrounding elements 401 and 402 are designated byreference signs 403, 404 and 405, where higher reference numeralscorrespond to higher distance from the element under analysis (element400). Picture-elements in the next layer (immediately surroundingelements 403-405) are designated by reference sign 406.

According to some embodiments of the present invention the methoddetermines that there is a local minimum of intensity at the location ofelement 400 if at least one, and more preferably each of the followingcriteria is met: (i) the intensity of element 400 is higher than theintensity of element 401; and (ii) the intensity value of element 400 ishigher than the intensity of element 403 divided by k, where k is apredetermined threshold. A typically value of k is between 1 and 2,e.g., 1.5.

In various exemplary embodiments of the invention adjacentpicture-element having identical intensity are checked to be localminimum in all eight directions. For example, suppose that theintensities of the two elements which are marked by rectangle 420 inFIG. 18 (element 400 and its nearest immediate neighbor 401 from theright side) are equal. In this case the method according to the presentembodiment decides that there is a local minimum at the location 400 ifthe intensity value of element 400 is lower than the intensity values ofeach of the 10 elements in the immediate layer surrounding those twoelements (the layer of picture-element between rectangle 420 andrectangle 422).

FIG. 16F shows patterns of local minima in the form of a two-dimensionalimage, in the embodiments in which the above search procedure isemployed.

Optionally, the method continues to 341 at which the method employs anoise reduction procedure. This can be done, for example, by searchingfor picture-elements which are identified as located in local extermabut which are isolated from other local extrema. These elements arepreferably declared by the method as noise. In various exemplaryembodiments of the invention noise picture-elements are assigned withtheir original intensity. FIG. 16G shows patterns of local minima in theform of a two-dimensional image, after the implementation of a noisereduction procedure of the present embodiments.

At 350 the method applies an interpolation procedure for generatingcontours between at least a few of the local intensity extrema. Themethod preferably searches the local extrema and decides according to apredetermined criterion or set of criteria whether or not to joinnon-continuous segments of local extrema. For example, the method canconnect two local intensity extrema if the distance between them is nothigher than two pixels. FIG. 16H shows patterns of local minima in theform of a two-dimensional image, after the implementation of the noisereduction procedure followed by the interpolation procedure of thepresent embodiments.

In various exemplary embodiments of the invention the generated contoursare identified as blood vessels. The method preferably issues a reportwhich includes the identified blood vessels. FIG. 16-I is an example ofa report which is in the form of a two-dimensional image showing thepatterns of the identified blood vessels. The identified blood vesselscan also be presented as a map of blood vessels.

It is to be understood that the presentation and reference to “images”in the above description is for the purpose of clarity and is not to beconsidered as limiting. The method of the present embodiments can beimplemented without displaying the data resulting from each operation inthe form of an image. Yet, the presentation of an image for at least afew of the operations is not excluded from the scope of the presentinvention.

Method 300 ends at 350.

Reference is now made to FIG. 19 which is a schematic illustration of anapparatus 500 for identifying blood vessels in a thermal image of asection of a living body, according to some embodiments of the presentinvention. Apparatus 500 can be implemented in a data processor or acomputer system and can be used for executing one or more of the methodsteps described above. Preferred data flow channels between the variouscomponents of apparatus 500 are shown as arrows in FIG. 19. It is to beunderstood, however, that some data flow channels are optional and maybe omitted, for example, and that the method also contemplates otherdata flow channels which, for clarity of presentation, are not shown inFIG. 19.

In some embodiments of the present invention apparatus 500 comprises aninput unit 502 for receiving the thermal image. Apparatus 500 preferablycomprises a convolution unit 504 which convolves the intensity data witha predetermined vessel shapes filter, a derivative calculator 506 whichcalculates local derivatives of the filtered data, a local intensityextrema searcher 508 which searches in the derivative data for localintensity extrema, and an interpolator 510 which applies aninterpolation procedure for generating contours between at least a fewof the local intensity extrema, and identifying the contours as bloodvessels as further detailed hereinabove.

In some embodiments of the present invention apparatus 500 comprises anormalization unit 512 which normalizes the intensity data, as furtherdetailed hereinabove. In some embodiments of the present inventionapparatus 500 further comprises an intensity data inverter 514 forinverting the intensity data by linear transformation, as furtherdetailed hereinabove. In some embodiments of the present inventionapparatus 500 comprises a masking unit 516 for masking the intensitydata so as to exclude at least a portion of the intensity data, asfurther detailed hereinabove. In some embodiments of the presentinvention apparatus 500 comprises a noise reduction unit 518 whichemploys a noise reduction procedure to exclude isolated local intensityextrema, as further detailed hereinabove.

Apparatus 50 preferably comprises an output unit 520 which issues areport regarding the patterns and locations of the identified bloodvessels. The report can be in the form of an image or a blood vessel mapas further detailed hereinabove.

Identification of blood vessels according to some embodiments of thepresent invention can be useful for the estimation of characteristicheat conduction of a body section. For example, when a series ofthermospatial representations of the body section are known, the presentembodiments can calculate the depth of one or more blood vessel sectionsand measure the rate of heat transfer to or from the blood vesselsection(s).

FIG. 20 is a flowchart diagram of a method suitable for estimatingcharacteristic heat conduction, according to various exemplaryembodiments of the present invention.

The method begins at 600 and continues to 601 at which a first dataacquisition (spatial and thermal) is performed while the body section isin a first shape referred to hereinafter as the “undeformed shape.” Themethod continues to 602 at which a first thermospatial representation isconstructed, and 603 at which the depth of one or more blood vesselsections is calculated using the first thermospatial representation.Calculation of depth from the thermospatial representation can be done,for example, by triangulation or any other technique known in the art.

The method subsequently proceeds to 604 in which a second dataacquisition is performed while the body section is in a second shapewhich is deformed with respect to the undeformed shape. A secondthermospatial representation is then constructed. While the shape isstill deformed, data is repeatedly acquired until the blood vesselssection(s) is in a steady thermal state (decision 605). The repetitionof data acquisition (process 604) can be done only for thermal datasince there is no change in the shape of the body section betweensuccessive acquisitions.

The method continues to 606 at which the thermal stabilization period isdetermined. Generally, the thermal stabilization period can be definedas the elapsed time between the deformation of the body shape and theonset of steady state. The method can also calculate the difference insteady state temperatures before and after deformation. The methodproceeds to 607 in which the second thermospatial representation is usedfor recalculating the depth of the same blood vessel section(s) so as todetermine the difference in the depths due to the deformation. Themethod then continues to 608 at which the thermal conductivity iscalculated based at least in part on the knowledge of the thermalstabilization period. In various exemplary embodiments of the inventionthe thermal conductivity is calculated using the Stefan-Boltzmann lawbased on the thermal stabilization period and the differences in depthsand steady state temperatures.

The method ends at 609.

As used herein the term “about” refers to ±10%.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to”.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention. To the extent thatsection headings are used, they should not be construed as necessarilylimiting.

What is claimed is:
 1. Apparatus for identifying blood vessels in athermal image of a section of a living body, the apparatus comprising: aconvolution unit, for convolving intensity data representing the thermalimage with a predetermined vessel shapes filter thereby to providefiltered data; a derivative calculator, for calculating, for eachpicture-element of said thermal image, calculating at least a firstlocal derivative of said filtered data along a first dimension and asecond local derivative of said filtered data along a second dimension,and selecting a highest of said first and said second local derivatives,thereby providing derivative data; a local intensity extrema searcher,for searching in said derivative data for local intensity extrema; andan interpolator, for applying an interpolation procedure for generatingcontours between at least a portion of said local intensity extrema, andidentifying said contours as blood vessels.
 2. The apparatus of claim 1,further comprising an intensity data inverter for inverting saidintensity data by linear transformation.
 3. The apparatus of claim 1,further comprising a masking unit for masking said intensity data so asto exclude at least a portion of said intensity data, said portioncorresponding to picture-elements not belonging to blood vessels.
 4. Theapparatus of claim 3, wherein said masking unit is operable to calculateat least one of: local minimum, local maximum and local average for eachpicture-element of the thermal image.
 5. The apparatus of claim 1,further comprising a normalization unit for normalizing said intensitydata.
 6. The apparatus of claim 1, further comprising a noise reductionunit which employs a noise removal procedure to exclude isolated localintensity extrema.
 7. A method of identifying blood vessels in a thermalimage of a section of a living body, the method comprising: convolvingintensity data representing the thermal image with a predeterminedvessel shapes filter thereby providing filtered data; for eachpicture-element of said thermal image, calculating at least a firstlocal derivative of said filtered data along a first dimension and asecond local derivative of said filtered data along a second dimension,and selecting a highest of said first and said second local derivatives,thereby providing derivative data; searching in said derivative data forlocal intensity extrema; and applying an interpolation procedure forgenerating contours between at least a portion of said local intensityextrema, and identifying said contours as blood vessels.
 8. The methodof claim 7, further comprising, prior to said convolution, invertingsaid intensity data by linear transformation.
 9. The method of claim 7,further comprising masking said intensity data so as to exclude at leasta portion of said intensity data, said portion corresponding topicture-elements not belonging to blood vessels.
 10. The method of claim9, wherein said masking comprises calculating at least one of: localminimum, local maximum and local average for each picture-element of thethermal image.
 11. The method of claim 7, further comprising normalizingsaid intensity data.
 12. The method of claim 7, further comprising,subsequently to said search for local intensity extrema, employing anoise reduction procedure for excluding isolated local intensityextrema.
 13. The method of claim 7, further comprising generating ablood vessel map based on said identified blood vessels.
 14. A method ofrecognizing an individual based on a body section of the individual,comprising: identifying blood vessels in a thermal image of the bodysection using the method of claim 7, so as to generate a blood vesselmap; searching a searchable database of blood vessel maps for a mapentry which is similar to said blood vessel map; and identifying theindividual based on said map entry.
 15. A method of estimatingcharacteristic heat conduction of a section of a living body,comprising: obtaining a series of thermospatial representationsdescribing the section of the living body while having at least twodifferent shapes; for each shape of said at least two different shapes,executing the method of claim 7 for identifying at least one bloodvessel in thermal data of a respective thermospatial representation andcalculating a depth of said at least one blood vessel; determiningthermal stabilization period for said at least one blood vessel; anddetermining the characteristic heat conduction based at least in part onsaid thermal stabilization period.